Metathesis ring-opening polymerization of norbornene monomers provides a variety of useful unsaturated cyclic olefin polymers such as norbornene dicarboximide polymers which exhibit advantageously high glass transition temperatures, low dielectric permittivity and good mechanical properties which commend their use in a variety of applications, e.g. in the electronics industry as substrates for supporting microelectronic circuits and as connectors. Because of the unsaturation in the polymer backbone, such polymers are not sufficiently stable to thermo-oxidative degradation for many high temperature applications. Although the oxidative stability of such polymers can be improved by conventional methods such as the incorporation of anti-oxidants, such additives often have an adverse effect on dielectric properties.